Rapper Jay-Z and his business partner own 40/40 Clubs in New York City, Las Vegas and Atlantic City. They also have plans to open more venues in Tokyo and Macau.

Jay-Z's launched his night club chain in New York two years ago. The $5 million trademark infringement lawsuit against Ortiz alleges:

Unjust enrichment and

False designation of sponsorship

Jay-Z's lawyer, Peter Raymond said he knows Ortiz has visited the 40/40 club in Manhattan at least twice. Raymond said he also has information as to the exact dates Ortiz visited the club.

In the lawsuit, Jay-Z is accusing the baseball player of causing "marketplace confusion" by using also registering a web site by the same name, www.fortyforty.net.

Typically, an important part of lawsuits alleging trademark infringement is whether the marks or names are "confusingly similar" to customers. This issue is frequently the key dispute in a trademark infringement case.

In this case the lawsuit claims that Ortiz used the name of Jay-Z's 40/40 Club without permission.

It also is not clear whether Jay-Z is seeking compensation, a club name change or both.